Glow-discharge transmitter



1,626,645 P. THOMAS GLOW DISCHARGE TRANSMITTER May 3, 1927.

Filed Nov. 1 1922 5 i 5 I ""u!4( .51 I

' I ,I 9 /z I I 7 l/ 4 Z Mlcro vhowe WITNESSES: I INVENTOR BY .7 I I ATTORNEY Patented May 3, 1927.

TED srars PHILLIPS THOMAS, OI EDGEWOOD, PENNSYLVAN IA, ASSIGNOR TO WESTINGHOUSE ELECTRIC &: MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

GLOW-DISCHARGE TRANSMITTER.

Application filed November 14, 1922. Serial No. 600,822.

My invention relates to telephone systems and ap aratus, having particular relation to sound-wave translatlng devices.

Broadly speaking, an important ob ect of my invention is to provide a translating device adapted to effect an energy interchange between a fiuid medium subject to vibratory motion and an electrical circuit carrying vibratory electrical currents.

More specifically, an object of my lnvention is to provide a translating device of the class described, wherein sound waves are faithfully translated into correspondingly modulated electrical energy without impairing the quality, tone and quantity of the translated energy.

Another object of my invention is to provide a translatin device of the class described above which is characterizedby its simplicity of design and operation and which lends itself to inexpensive quantity production methods of manufacture and wherein the several parts may easily be made by existing automatic machinery and may readily be assembled with a minimum expenditure of time and money.

A further object of my invention is to provide an improved translating device of the glow-discharge type wherein the-intensity of response to pressure variations is independent of the frequency of such varia-' tions.

A still further object of my invention is to provide a glow-dischar etranslatin device which is unaffected by drafts 0 air currents and which remains permanently in a sensitive state.

A glow discharge which is established between spaced positive and negative electrodes may comprise the followin portions. a positive or anode column, whic i is in immediate contact with the positive electrode; a Faraday dark space; a negative light; a cathode dark space; and a cathode glow which is in immediate contact with the negative electrode. As a result of considerable experimental work, I have found that the sensitivity of the portion of the dis charge including the positive column varies with the frequency of impinging sound waves and that the sensitivity of the remaining' ortions of thedischargeyincludingthe arada dark space, the cathode glow, .the catho e dark space and the negarespectively, to the negative discharge electrode and to a third electrode which is positioned in the discharge immediately adjacent to the end of the positive column. The

third electrode is provided with an aperture through which the end of the positive col: umn extends, as will be more specifically described hereinafter.

I have further found that the uality of the translated energy, as well as the stability of the discharge in the presence of air currents, is reatly improved by shielding the anode co umn from sound waves durin the normal operation of my device, as wil be explained more fully hereinafter.

Other objects and applications of my invention, as well as details of construction and operation whereby my invention may be practiced, will be a parent from the following description, w en taken in connec- 7 tion with the accompanying drawing, where- Figure 1 is a diagrammatic view ofcirs cuits and apparatus embodying my invention;

Figure 2 is a greatly enlarged detail view of the discharge electrodes of Fig. 1, together with a third electrode and means for shielding the anode column. In one form of embodiment of m tion shown in 'the drawing, a pair 0 co electrodes 1 and 2, having spaced sparfimg tips 3 and 4, respectively, terminating in fine points, are connected by conductors 5 and 6, respectively,-to the plus and minus terminals of a source of direct-current energy (not shown). The sparking tips 3 and 4 are preferably made of copper because of the fact that a glow discharge may be easily inven in operation, in comparison with other well known materials where in some cases it is even impossible to establish a glow discharge. For instance, so far, it has been found impossible to establish a'glow discharge between electrodes of man anese, iron, nickel, .carbon, aluminum or mo ybde- 'num, while the discharge, which was estab- I of an inch for a system having the constants just mentioned, a discharge is established between the two electrodes 1 and 2, which differs from the ordinary arc-type of discharge, in the following .important respects the electrodes are relatively cool; there is substantially no vaporization or melting or burning of the electrodes; the customary hot-spot characteristic of the ordinary arc is absent; and the discharge, when formed between certain materials, as copper, takes place in a steady smooth and unfluctuating manner.

The latter operating characteristic of the glow discharge is of special importance inasmuch as fluctuations in the operation of the discharge may be such as to cause potential or current variations which are comparable, in magnitude, to the variations caused by sound waves, as will be apparent in the li ht of the following description.

The g ow discharge which is established between the electrodes 1 and 2 comprises the following portions arranged in their respec tive order between the negative elctrode 2 and the positive electrode 1; namely, a cathode glow 8, which is in immediate contact with the negative electrode 2, a cathode dark space 9, also known as Crookes dark space, a negative light 11; a Faraday dark space 12, and a positive column 13, which terminates on the tip 3 of the positive electrode 1, al] as illustrated in Fig. 2.

When the discharge is once established and when the current therethrough is maintained substantially constant, the potential drop there across varies with pressure and also with the frequency of the pressure variations in the higher portions of the audibilit range. The result of such variations in t e sensitiviy of the discharge with fre,-. quency is to cause the distortion of the higher notes in the audible-frequency range. After considerable experimental work, as

hereinbefore stated, it-was found that it is only. the ortion of the dischar e including the positive column which varies in sensitivity with changes in the frequency of the pressure variations while the remaining portion of the discharge was "found to be substantially insensitive to changes in the frequenc of the pressure variations.

Accor ingly, apparatus was arranged which made possible the detection of pressure variations in the portion of the dis-- charge between the free end of the positive column 13 and the negative electrode 2. The apparatus comprises a third electrode 14 disposed in the discharge just at the free end of the positive column 13, and a repeater device 14m The third electrode 14 is provided with a perforation 15 on the ordcrpl' .014 inch in diameter which is positioned in the path of the discharge.

The alternating component of voltage which is established between the third electrode 14 and the negative electrode 2 in the presence of sound waves may be translated into amplified currents of similar wave form by impressing the same, through conductors 15 and 16, upon the grid and filament elements 17 and 18, respectively, of the repeater device 14a, which includes in addition, a plate element 19. U

A condenser 21 having a negligible impedance to currents of sound-wave frequency, is included in the grid conductor-15 and serves to prevent the so-callcd quiet voltage drop in the glow discharge between the third electrode 14 and the negative'electrode 2 from operating to block thetube 14a. A grid-leak resistor 22 may be included in shunt relation to the grid and filament elements 17 and 18, respectively, in order to control the intensity of the negative charges which are accumulated on the grid 17.

A late-filament circuit for the tube 14a inclu es a source 23 of direct-current energy and a high-impedance resistance coupling device 24. The potential variations, which are established across the resistor 24 when the glow discharge is subjected to pressure variations, as, for instance, those caused by sound waves, may be impressed by conductors 25 and 26 upon the input elements of a second amplifying device (not shown) or other circuit arrangement designed to employ such n'iodulated energyr In order to insure that the discharge will be a glow discharge and will continue to be a glow discharge, and not change into an are, I find that the-source of potential must be high and that a current limiting device must be used. In addition to the specific dimensions already stated herein the following actual constructions are noted. In one specific embodiment of my invention,I employed a source of somewhat more than 4000 volts with a resistance in series between it and the discharge device of approximately one megohm. In another specific embodiment of this invention, I employed a source of 4200 volts, together with a current limiting device which restricted the current to one milliampere. The current limiting device used in this instance was a saturation tube.

A characteristic difference between the glow discharge and the are is found in the relation of current to voltage. In the arc the current is much greater and the voltage much smaller than in the glow discharge. Another characteristic difference is that with the glow discharge the electrodes are relatively cool, never becoming incandescent, while with an arc the electrodes are hot and the cathode is usually more incandescent than any portion of the are itself.

During experimental work, it was found that the sensitivity of the glow discharge, as a translating device, decreased as the diameter of the perforation 15 was increased, and that best results were obtained by employing a perforation, the diameter of which was small in comparison to that of the positive column 13. As shown in Fig. 2, the free end ofthe positive column 13 extends through the perforation 15 without engaging the walls thereof, forming a small tip portion 27. After prolonged operation, the third electrode 14 becomes slightly heated but does not assume the temperature of the glow discharge.

As hereinbefore stated, it was found that still further improved results were obtained by shielding the anode column 13 from the effects of air currents and sound waves, and I have shown, in Figs. 1 and 2, one particular arrangement for carrying this into practice. The arrangement shown comprises a tubular member 28 of insulating material which is supported from one end by the positive electrode 1. The remaining end may carry the third electrode 14.

In view of the foregoing, it is apparent that my invention provides a translating or amplifying device which is characterized by its simplicity of design and operation and by the absence of moving parts. Other advantages 'will be apparent from a study of the foregoing description.

While I have described my invention as embodied in a particular circuit arrangement having specific values, it is apparent that various changes and modifications may be made therein without departing from the spirit of my invention. I desire, therefore, that only such limitations shall be imposed thereon as are demanded by the prior art or are specifically set forth in the appended claims.

I claim as my invention:

1. In combination, a pair of spaced electrodes, means for maintaining between said electrodes a discharge of the character which has a dark space and a glowing space means for shieldin a predetermined portion only of said disc arge from pressure variations in the vicinity of said discharge.

2. A translatin device comprising a pair of spaced electro es, means for maintaining between said electrodes a discharge of the character which has a dark space and glowing spaces, including a positive column, said electrodes being exposed to the pressure of the atmosphere, means for preventing the air immediately adjacent the positive column from departing, said means leaving the air immediately adjacent the remainder of the discharge free to depart.

3. An amplifying device comprising a pair of spaced electrodes, means for maintaining between said electrodes a discharge of the character which has a dark space and glowing spaces including a positive column, said electrodes being open to the air and means for enclosing said positive column in such manner as to shield the same from pressure variations incident to the presence of sound waves said means leaving the other portions of said glow discharge exposed to said variations.

4. In an electrical system, the combination with a pair of electrodes constituting the positive and negative terminals of a discharge device, of means for maintaining-between said electrodes a discharge of the character which has a dark space and a glowing space, said discharge including a portion wherein the voltage-current'characteristic varies with the frequency of pressure variations thereabout and also including a portion wherein the voltage-current characteristic is substantially independent of the frequency of the pressure variations thereabout and means responsive to variations in the voltage-current characteristic of only the latter portion.

5. In an electrical system, the combination with a pair of electrodes constituting the positive and negative terminals of a discharge device, of means for maintaining between said electrodes a discharge of the character which has a dark space and glowing spaces including a positive column, said electrodes being open to the air and translating means responsive only to variations in the characteristic of only the remaining portions of said discharge.

6. In an electrical system, the combination with a pair of spaced electrodes open to the atmosphere and constituting the positive and negative terminals of a discharge device, of means for maintaining between said electrodes a discharge of the character which has a dark space and a glowing space, a

third electrode and said negative electrode.

7. In an electricalsystem, the combination with a pair of spaced electrodes constituting the positive and negative terminals of a discharge device, of means for maintaining between said electrodes a discharge of the character which has a dark space and a glowing space, a third electrode embracing a portion of said discharge and a translatmg device having input terminals connected to said third electrode and said negative electrode, respectively.

8. In an electrical system, the combination with a air of spaced electrodes constituting the positive and negative terminals of a discharge device, of means for maintaining a discharge therebetween of the character which has a positive column and a Faraday dark space, a third electrode having a perforationv therein positioned in said discharge immediately adjacent to the boundary line between said positive column and said Faraday dark space, and a repeater circuit connected across said third electrode and said negative electrode.

9. In an electrical system, the combination with a pair of spaced electrodes constituting the positive and negative terminals of a dis charge device, of means for maintaining a discharge therebetween of the character which has a positive column and a Faraday dark space, a third electrode having a perforation therein disposed in said positive column near the boundary line between said positive column and said Faraday dark space, and a translating device operatively associated with said third electrode and said negative electrode for converting variations in the voltage-current characteristic of the discharge therebetween into amplified current variations.

10. In an electrical system, the combination with a pair of spaced electrodes constituting the positive and negative terminals of a discharge device, of means for maintaining a discharge therebetween of the character which has a positive column and a Faraday dark space, a third electrode disposed intermediate said pair of electrodes near the end of said positive column adjacent to said Faraday dark space, said third electrode having a perforation of relatively small diameter in comparisonto that of said positive column, the end of said column extending through said perforation, and a repeater device having its input circuit connected across said third electrode and said negative electrode.

11. A translating device comprising a pair of spaced electrodes, means for maintaining between said electrodes a discharge of .the

' character which has a dark space and glowing spaces including a positive column, said electrodes being open to the air, means for shielding said positive column from the ellects of pressure variations in the vicinity of the discharge, a third electrode interposed between said pair of electrodes near the .free end of said ositive column and translating means having an input circuit connected across said third electrode and one of said pair of electrodes.

12. In an electrical system, the combination with a pair of electrodes constituting the positive and negative terminals of a discharge device, of means for maintaining between said electrodes a discharge of the character which has a dark space and glowing space including a positive column, said electrodes being open to the air, means for shielding a part, but not all, of said discharge from pressure variations in the immediate vicinity of said discharge, said part including said positive column, a third electrode interposed between said pair of electrodes near the free end of said positive column, said third electrode having a perforation in the path of said discharge, and translating means having an input circuit connected across said third electrode and one of said pair of electrodes.

13. In an electrical system, the combination with a pair of electrodes constituting the positive and negative terminals of a discharge device, of means for maintaining between said electrodes a discharge of the character which has a dark space and glowing spaces including a positive column, said electrodes being open to the air, means for enclosing the space immediately surrounding said positive column to shield said column from pressure variations, a third electrode disposed intermediate said pair of electrodes adjacent to the free end of said positive column, said third electrode having a perforation for receiving said discharge, and translating means having an input circuit connected across said third electrode and one of said pair of electrodes.

14. In an electrical system, the combination with a pair of electrodes constituting the positive and negative terminals of a discharge device, of means for maintaining between said electrodes a discharge of the character which has a dark space and glowing spaces including a positive column, said electrodes being open to the air, means for maintaining the currents through said discharge substantially constant, means for enclosing the space immediately surrounding said positive column to shield said column from pressure variations, a third electrode disposed intermediate said pair (f electrodes adj accnt to the free end of said positive column, said third electrode having a perforation for receiving said discharge, and translating means having an input circuit connected across said third electrode and one of said pair of electrodes.

15. A sound-wave translating device comprising an apparatus for producing a discharge in the open air and maintaining said discharge of the character which has a dark space and glowing spaces including a positive column, means for minimizing the efiect of the positive column upon the characteristics of the discharge in the pres-' ence of sound-wave disturbances, and means responsive to the changes in a characteristic mg a positive column, means responsive to the changes in a characteristic of the dlscharge resulting from said pressure variations, and means for minimizing the effect of the positive column upon the characteristics of the discharge in the presence of soundwave disturbances.

17, In a sound translating device, a, pair I of. spaced electrodes and a source of electromotive force suitable for maintaining a glowdischarge between said electrodes, a portion of, the space between said electrodes being open to the sound waves.

18.111 :1 sound translating device, a pair of'spaced' electrodes and a source of electromotive force suitable for maintaining a glow discharge between said electrodes, a portion of the space between said electrodes bein open to the sound waves and a portion o said space being shielded from them.

In testimony whereof, I have hereunto subscribed'my. name this 10th day of Novem:

ber, 1922.

PHILLIPS THOMAS. 

